Ozone plenum as UV shutter or tunable UV filter for cleaning semiconductor substrates

ABSTRACT

A quartz window with an interior plenum is operable as a shutter or UV filter in a degas chamber by supplying the plenum with an ozone-containing gas. Pressure in the plenum can be adjusted to block UV light transmission into the degas chamber or adjust transmittance of UV light through the window. When the plenum is evacuated, the plenum allows maximum transmission of UV light into the degas chamber.

BACKGROUND

During plasma processing of semiconductor substrates wherein thesemiconductor substrates are exposed to halogen-containing processgases, a residue of the process gases, e.g. a residue containingbromine, can remain on surfaces of the semiconductor substrates. Suchresidue can cause defects in the semiconductor substrates in downstreamprocessing steps, and can contaminate other semiconductor substrates inthe processing pipeline. Therefore, it is desirable to remove suchresidue from the semiconductor substrates in a degas chamber.

SUMMARY

A quartz window of a degas chamber in which semiconductor substrates arecleaned with an ozone-containing gas under illumination of UV light, thequartz window comprising: a bottom surface, a top surface and a sidewallextending between the bottom surface and the top surface; a plenumbetween the top and bottom surfaces; and at least one gas passage influid communication with the plenum. The quartz window can be mountedover an opening in a top wall of the degas chamber. The plenum covers atleast the entire area of the quartz window that overlies the opening.The plenum can be supplied with an ozone-containing gas with a suitableozone partial pressure to block and/or tune UV light transmissionthrough the quartz window.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows a schematic cross section of a degas chamber with a quartzwindow according to an embodiment.

FIG. 2 shows a schematic cross section of a degas chamber with a quartzwindow according to another embodiment.

FIG. 3 shows UV (254 nm wavelength) transmittance through a plenum as afunction of the product of ozone partial pressure therein and a heightthereof.

DETAILED DESCRIPTION

Described herein is a quartz window with a gas plenum between upper andlower surfaces thereof to function as a UV shutter or adjustable UVfilter. In one embodiment, the quartz window with a plenum is identicalin outside dimensions and shape as, and mounted on a degas chamber thesame way as, the quartz window disclosed in commonly assigned U.S.patent application Ser. No. 12/607,659, the disclosure of which ishereby incorporated by reference.

As shown in FIG. 1, a degas chamber 100 comprises a vacuum chamber wall10, made of a metallic material such as aluminum. A quartz window 130 isclamped to a top wall of the chamber wall 10 by any suitable arrangementsuch as a plurality of clamps 40 so as to overlie a top opening in thetop wall larger than a semiconductor substrate such as a wafer to becleaned in the chamber. The quartz window 130 is preferably made ofsynthetic quartz for its high transmission of UV light. Synthetic quartzis typically untwinned and produced in an autoclave via the hydrothermalprocess. A continuous O-ring 35 between the quartz window 130 and thechamber wall 10 provides a vacuum seal. A UV lamp assembly 80 isdisposed above the quartz window 130, the UV lamp assembly 80 comprisinga plurality of parallel UV lamps 85.

The quartz window 130 is configured to be mounted on the top of thedegas chamber 100 in which UV light from the UV lamp assembly 80 cantransmit through the quartz window 130 while ozone gas is flowed in thedegas chamber 100 to remove halogen-containing residues from asemiconductor substrate 50 such as a 300 mm wafer supported in the degaschamber 100.

During processing in the degas chamber 100, the degas chamber 100 isevacuated by a vacuum pump 60 and the semiconductor substrate 50 istransferred through a loading door 20 in the chamber wall 10 and placedon a suitable support such as a plurality of substrate support pins 55.An ozone-containing gas flows from an ozone source 70 into the degaschamber 100. The gas preferably contains a small amount of nitrogen gas(e.g. 0.1 to 0.5 wt %). The gas pressure in the degas chamber 100 ispreferably maintained from 100 mTorr to 10 Torr, more preferably from0.5 to 1.5 Torr, with an ozone partial pressure preferably from 0.0005to 1 Torr, more preferably from 0.0025 to 0.33 Torr, most preferablyfrom 0.05 to 0.08 Torr. The UV lamp assembly 80 irradiates thesemiconductor substrate 50 through the quartz window 130 with UV lightpreferably of a wavelength of 254 nm and intensity between 0.05 and 5W/cm², for a period of 10 seconds to 1 minute. Ozone gas absorbs UVlight and decomposes into O radicals (atomic oxygen) which react withhalogen-containing residues such as bromine or chlorine on thesemiconductor substrate 50. The reaction products are gaseous and areevacuated from the degas chamber 100 by the vacuum pump 60.

During a process of transporting the semiconductor substrate 50 into andout from the degas chamber 100, it is desirable to block UV light of theUV lamp assembly 80 from entering the degas chamber 100. However, tominimize delay in processing substrates and to prevent premature failureof UV lamps 85, it is desirable that UV lamps 85 in the UV lamp assembly80 remain powered rather than being switched on and off for eachsubstrate transport.

In a first embodiment as shown in FIG. 1, the quartz window 130 in adegas chamber 100 has a plenum 140 in an interior. The plenum 140 atleast covers an opening in the top wall through which UV light from theUV lamp assembly 80 passes into the chamber 100. The ozone source 70 isconnected to the degas chamber 100 through a gas line 66, gas flowthrough which can be controlled by a valve 65. The degas chamber 100 isconnected to an inlet of the vacuum pump 60 through a gas line 76, gasflow through which can be controlled by a valve 75. An outlet of thevacuum pump 60 is connected via a gas line 67 to an ozone destroyingunit 90. The ozone destroying unit 90 is operable to destroy ozone (e.g.by converting ozone to oxygen gas) in gas flowing therethrough beforereleasing the gas to the atmosphere. The ozone source 70 is alsoconnected to an inlet of another vacuum pump 61 through a gas line 167,gas flow through which can be controlled by a valve 166. The plenum 140is connected to an inlet of the vacuum pump 61 through a gas line 168,which branches off line 167, and gas flow through which can becontrolled by a valve 165. An outlet of the vacuum pump 61 is connectedvia a gas line 169 to the ozone destroying unit 90.

The plenum 140 can be supplied with a suitable amount ofozone-containing gas effective to absorb UV light from the UV lamps 85when UV light is not needed in the degas chamber 100, such as during theprocess of transporting the substrate 50 into and out of the degaschamber 100. When UV light is needed for a degas process, the plenum 140is evacuated to allow UV light from the UV lamps 85 to pass through thequartz window 130 and reach the interior of the degas chamber 100. Thevalves can be flow control valves which can close or open to a range ofvalve positions to control flow rate therethrough. A controller 1000 isoperable to close valves 166, 165, 65 and 75 and adjust valve positionsof valves 166, 165, 65 and 75, adjust the ozone source 70 and gaspressure in the plenum 140 and the chamber 100.

In a second embodiment as shown in FIG. 2, the quartz window 230 in adegas chamber 200 has a plenum 240 in an interior. The plenum 240 atleast covers an opening in the top wall through which UV light from theUV lamp assembly 80 passes into the chamber 200. The ozone source 70 isconnected to the degas chamber 200 through a gas line 266, gas flowthrough which can be controlled by a valve 265. The degas chamber 200 isconnected to an inlet of the vacuum pump 260 through a gas line 276, gasflow through which can be controlled by a valve 275. An outlet of thevacuum pump 260 is connected via a gas line 216 to the ozone destroyingunit 90. The ozone source 70 is also connected to an inlet of the plenum240 through a gas line 286, gas flow through which can be controlled bya valve 285. An outlet of the plenum 240 is connected to the pump 260through a gas line 296, gas flow through which can be controlled by avalve 295.

The plenum 240 can be supplied with a suitable amount ofozone-containing gas effective to absorb UV light from the UV lamps 85when UV light is not needed in the degas chamber 200, such as during theprocess of transporting the substrate 50 into and out of the degaschamber 200. When UV light is needed for a degas process, the plenum 240is evacuated to allow UV light from the UV lamps 85 to pass through thequartz window 230 and reach the interior of the degas chamber 200. Thevalves can be flow control valves which can close or open to a range ofvalve positions to control flow rate therethrough. A controller 1000 isoperable to close valves 285, 265, 275 and 295 and adjust valvepositions of valves 285, 265, 275 and 295, adjust the ozone source 70and gas pressure in the plenum 240 and the chamber 200.

Transmittance of UV light through the plenum 140/240 can be calculatedby the Beer-Lambart Law:

$\begin{matrix}{\frac{l_{t}}{l_{0}} = {\mathbb{e}}^{- {cPd}}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

Wherein I₀ is intensity of UV light before entering the plenum 140/240;I_(t) is intensity of transmitted UV light through the plenum 140/240; Pis partial pressure of ozone gas in the plenum 140/240; c is a constantof about 130/atm/cm for UV light with a wavelength of 254 nm; and d is aheight of the plenum 140/240 through which UV light passes to reach theinterior of the chamber 100/200.

FIG. 3 shows dependence of UV transmittance at 254 nm wavelength throughthe plenum 140/240 on the product of P and d, according to Eq. 1. The xaxis is the product of P and d. The y axis is transmittance of UV lightat 254 nm wavelength. From FIG. 3 and Eq. 1, desired ozone partialpressure P in the plenum 140/240 can be deduced from the height d of theplenum 140/240 and desired transmittance. For example, if 0.1%transmittance is desired, and the height d is 1 cm, then desired ozonepartial pressure P is about 40 Torr. The product of P and d ispreferably from 4 to 53 cm·Torr. An upper wall and a lower wall of thequartz window 130/230 that enclose the plenum 140/240 have thicknessessufficient to withstand pressure differences between the vacuum pressurein the plenum 140/240, the vacuum pressure in the chamber 100/200 andatmosphere pressure pressing on the outside of the window. Preferablythe upper wall and the lower wall each have a thickness of at least 5mm, preferably at least 9 mm.

A cycle of an exemplary degas process comprises: (a) transporting thesemiconductor substrate 50 into the degas chamber 100/200; (b) supplyingthe interior of the degas chamber 100/200 with an ozone-containing gaswith a suitable ozone partial pressure (e.g. 0.0005 to 1 Torr); (c)evacuating the plenum 140/240; (d) generating O radicals in the chamberby irradiating the ozone-containing gas in the degas chamber 100/200with UV light directed into the chamber by a UV light assembly 80through the quartz window 130/230; (e) forming volatile byproducts byreacting halogen-containing residues on the semiconductor substrate 50with the O radicals for a suitable time period (e.g. 15 sec-60 sec) andevacuating the volatile byproducts from the chamber; (f) supplying theozone-containing gas to the plenum 140/240 and adjusting ozone partialpressure in the plenum 140/240 with the controller 1000 to essentiallyblock the UV light from the UV light assembly 80 (e.g. withtransmittance of no more than 0.1% through the quartz window 130/230);(g) evacuating the degas chamber 100/200; (h) transporting thesemiconductor substrate 50 out of the degas chamber 100/200; (i)repeating steps (a)-(h) with another semiconductor substrate.

In the first embodiment, the controller 1000 can be used to control thevalves to supply gas to and evacuate gas from the degas chamber 100 andthe plenum 140 in the exemplary degas process above. For example: (a)closing the valves 65, 75 and 166, opening the valve 165 with thecontroller 1000 to supply the ozone-containing gas to the plenum 140 andadjusting ozone partial pressure in the plenum 140 with the controller1000 to essentially block the UV light; (b) maintaining valve 65 closedand closing valve 165, opening valves 75 and 166 with the controller1000 to evacuate the degas chamber 100; (c) transporting a semiconductorsubstrate into the degas chamber 100; (d) maintaining valve 65 closed,maintaining valves 166 and 75 open, and opening valve 165 with thecontroller 1000 to evacuate the plenum 140; (e) maintaining valve 75open, and closing valves 166 and 165, opening the valve 65 with thecontroller 1000 to supply the degas chamber 100 with an ozone-containinggas; (f) generating O radicals in the chamber 100 by irradiating theozone-containing gas in the degas chamber 100 with UV light through thequartz window 130; (g) forming volatile byproducts by reactinghalogen-containing residues on the semiconductor substrate with the Oradicals for a time period (e.g. 15 sec-60 sec) and evacuating thevolatile byproducts from the chamber 100; (h) maintaining valve 166closed, closing valves 65, 75 and opening the valve 165 with thecontroller 1000 to supply the ozone-containing gas to the plenum 140 andadjusting ozone partial pressure in the plenum 140 with the controller1000 to essentially block the UV light; (i) maintaining valve 65 closed,closing valve 165, opening the valves 75 and 166, with the controller1000 to evacuate the degas chamber 100; (j) transporting thesemiconductor substrate out of the degas chamber 100; (k) repeatingsteps (a)-(j) with another semiconductor substrate.

In the second embodiment, the controller 1000 can be used to control thevalves to supply gas to and evacuate gas from the degas chamber 200 andthe plenum 240 in the exemplary degas process above. For example: (a)closing the valve 265, opening the valves 275, 285 and 295 with thecontroller 1000 to evacuate the degas chamber 200 and to supply theozone-containing gas to the plenum 240 and adjusting ozone partialpressure in the plenum 240 with the controller 1000 to essentially blockthe UV light; (b) transporting a semiconductor substrate into the degaschamber 200; (c) closing the valve 285, maintaining valves 275 and 295open and opening valve 265 with the controller 1000 to supply the degaschamber 200 with an ozone-containing gas and to evacuate the plenum 240;(d) generating O radicals in the chamber 200 by irradiating theozone-containing gas in the degas chamber 200 with UV light through thequartz window 230; (e) forming volatile byproducts by reactinghalogen-containing residues on the semiconductor substrate with the Oradicals for a time period (e.g. 15 sec-60 sec) and evacuating thevolatile byproducts from the chamber 200; (f) closing the valve 265,maintaining valves 275 and 295 open and opening valve 285 with thecontroller 1000 to evacuate the degas chamber 200 and to supply theozone-containing gas to the plenum 240 and adjusting ozone partialpressure in the plenum 240 with the controller 1000 to essentially blockthe UV light, and then (g) transporting the semiconductor substrate outof the degas chamber 200; (h) repeating steps (a)-(g) with anothersemiconductor substrate.

By adjusting the ozone partial pressure P in the plenum 140/240,transmittance through the quartz window 130/230 can be tuned, i.e. thequartz window 130/230 can be functional as a tunable UV filter.

A cycle of another exemplary degas process comprises: (a) transportingthe semiconductor substrate 50 into the degas chamber 100/200; (b)supplying the degas chamber 100/200 with an ozone-containing gas with asuitable ozone partial pressure (e.g. 0.0005 to 1 Torr); (c) adjustingthe ozone partial pressure in the plenum 140/240 such that UV lighttransmittance through the quartz window 130/230 reaches a desired value;(d) generating O radicals in the chamber by irradiating theozone-containing gas in the degas chamber 100/200 with UV light directedinto the chamber by the UV light assembly 80 through the quartz window130/230; (e) forming volatile byproducts by reacting halogen-containingresidues on the semiconductor substrate 50 with the O radicals for asuitable time period (e.g. 15 sec-60 sec) and evacuating the volatilebyproducts from the chamber; (f) adjusting the ozone partial pressure inthe plenum 140/240 to essentially block the UV light (e.g. withtransmittance of no more than 0.1% through the quartz window 130/230);(g) evacuating the degas chamber 100/200; (h) transporting thesemiconductor substrate 50 out of the degas chamber 100/200; (i)repeating steps (a)-(h) with another semiconductor substrate.

The quartz window 130/230 can also be used to compensate for reductionof UV light radiant flux (i.e. total power of UV radiation) from the UVlamp assembly 80 as the UV lamps 85 age.

A cycle of yet another exemplary degas process comprises: (a)transporting the semiconductor substrate 50 into the degas chamber100/200; (b) measuring UV light radiant flux from the UV lamp assembly80 with a UV light sensor 2000; (c) supplying the degas chamber 100/200with an ozone-containing gas with a suitable ozone partial pressure(e.g. 0.0005 to 1 Torr); (d) adjusting with the controller 1000 theozone partial pressure in the plenum 140/240 based on the measured UVlight radiant flux to compensate for changes of the UV light radiantflux from the UV lamp assembly 80 such that UV light radiant fluxthrough the quartz window 130/230 is adjusted to a desired value; (e)generating O radicals in the chamber by irradiating the ozone-containinggas in the degas chamber 100/200 with UV light directed into the chamberby the UV light assembly 80 through the quartz window 130/230; (f)forming volatile byproducts by reacting halogen-containing residues onthe semiconductor substrate 50 with the O radicals for a suitable timeperiod (e.g. 15 sec-60 sec) and evacuating the volatile byproducts fromthe chamber; (g) adjusting the ozone partial pressure in the plenum140/240 with the controller 1000 to essentially block the UV light (e.g.with transmittance of no more than 0.1% through the quartz window130/230); (h) evacuating the degas chamber 100/200; (i) transporting thesemiconductor substrate 50 out of the degas chamber 100/200; (j)repeating steps (a)-(i) with another semiconductor substrate.

The plenum 140/240 can be made by various manufacturing techniques. Forexample, the plenum 140/240 can be made by fusing two quartz plateshaving the plenum and at least one passage communicating with the plenummachined therein together, or by mechanically clamping two quartz platestogether with a resilient seal ring (e.g. rubber o-ring) sandwichedtherebetween to form plenum 140/240. The passage communicating with theplenum formed by the O-ring can be drilled through the outer plate andsuitable connections can be provided to the ozone-supplying and vacuumlines. The plates need to have thicknesses suitable to withstand thevacuum force acting on the inside of the window 130/230 due to thevacuum in the chamber and atmospheric pressure acting on the outside ofthe window 130/230.

Advantages of the quartz window 130/230 with an interior plenum 140/240include use of the quartz window 130/230 as a UV shutter or anadjustable UV filter without any mechanical moving parts or actuationmechanism that can occupy valuable space above the quartz window 130/230and/or be unreliable after repeated use. In addition, because the quartzwindow 130/230 lacks mechanical moving parts and an actuation mechanism,the UV lamps 85 can be placed very close to the quartz window 130/230and thus enhances UV light intensity at the substrate surface in thedegas chamber 100/200.

While the quartz window 130/230 with the plenum 140/240 has beendescribed in detail with reference to specific embodiments thereof, itwill be apparent to those skilled in the art that various changes andmodifications can be made, and equivalents employed, without departingfrom the scope of the appended claims. For example, the quartz windowcan have any suitable shape to accommodate different designs of a degaschamber; the shape and location of the plenum in the quartz window canvary as long as the plenum covers substantially the entire area of thequartz window that is exposed to UV light from the UV lamps.

We claim:
 1. A method of processing a semiconductor substrate,comprising: (a) transporting a semiconductor substrate into a degaschamber comprising a quartz window removably mounted over an opening ina top wall of the degas chamber and a UV lamp assembly disposed abovethe quartz window, the quartz window including a plenum and at least onegas passage in fluid communication with the plenum; (b) supplying thedegas chamber with an ozone-containing gas; (c) evacuating the plenum;(d) generating O radicals in the chamber by irradiating theozone-containing gas in the degas chamber with UV light through thequartz window; (e) forming volatile byproducts by reactinghalogen-containing residues on the semiconductor substrate with the Oradicals for a time period and evacuating the volatile byproducts fromthe chamber; (f) supplying the ozone-containing gas to the plenum andadjusting ozone partial pressure in the plenum to essentially block theUV light; (g) evacuating the degas chamber; (h) transporting thesemiconductor substrate out of the degas chamber; (i) repeating steps(a)-(h) with another semiconductor substrate.
 2. The method of claim 1,wherein the quartz is synthetic quartz and/or the quartz window includesa first gas passage in fluid communication with the plenum operative toallow supply of the ozone-containing gas to the plenum and a second gaspassage in fluid communication with the plenum operative to allowevacuation of the plenum.
 3. The method of claim 1, wherein the plenumis located between two quartz plates with a vacuum seal therebetweendefining the plenum, a pair of quartz plates bonded together andmachined with the plenum between opposed surfaces of the plates, or apair of quartz plates bonded to a quartz ring defining the plenumbetween opposed surfaces of the plates and inwardly of the ring.
 4. Themethod of claim 1, wherein the quartz window is removably mounted by aplurality of clamps, and an O-ring disposed between the quartz windowand the upper surface of the degas chamber to provide a vacuum seal. 5.The method of claim 1, wherein the plenum covers the entire opening inthe top wall through which the semiconductor substrate is exposed to UVlight from the UV lamp assembly.
 6. A method of processing asemiconductor substrate, comprising: (a) transporting a semiconductorsubstrate into a degas chamber comprising a quartz window removablymounted over an opening in a top wall of the degas chamber and a UV lampassembly disposed above the quartz window, the quartz window including aplenum and at least one gas passage in fluid communication with theplenum; (b) supplying the degas chamber with an ozone-containing gas;(c) adjusting an ozone partial pressure in the plenum such that UV lighttransmittance through the quartz window is adjusted to a desired value;(d) generating O radicals by irradiating the ozone-containing gas in thedegas chamber with UV light through the quartz window; (e) formingvolatile byproducts by reacting halogen-containing residues on thesemiconductor substrate with the O radicals for a time period andevacuating the volatile byproducts from the chamber; (f) adjusting theozone partial pressure in the plenum to essentially block the UV light;(g) evacuating the degas chamber; (h) transporting the semiconductorsubstrate out of the degas chamber; (i) repeating steps (a)-(h) withanother semiconductor substrate.
 7. A method of processing asemiconductor substrate, comprising: (a) transporting a semiconductorsubstrate into a degas chamber comprising a quartz window removablymounted over an opening in a top wall of the degas chamber and a UV lampassembly disposed above the quartz window, the quartz window including aplenum and at least one gas passage in fluid communication with theplenum; (b) measuring UV light radiant flux from the UV lamp assemblywith a UV light sensor; (c) supplying the degas chamber with anozone-containing gas; (d) adjusting an ozone partial pressure in theplenum based on the measured UV light radiant flux such that UV lightradiant flux through the quartz window is adjusted to a desired value;(e) generating O radicals in the degas chamber by irradiating theozone-containing gas in the degas chamber with UV light through thequartz window; (f) forming volatile byproducts by reactinghalogen-containing residues on the semiconductor substrate with the Oradicals for a time period and evacuating the volatile byproducts fromthe chamber; (g) adjusting the ozone partial pressure in the plenum to apartial pressure effective to essentially block the UV light andevacuating the degas chamber; (h) evacuating the degas chamber; (i)transporting the semiconductor substrate out of the degas chamber; (j)repeating steps (a)-(i) with another semiconductor substrate.
 8. Themethod of claim 1, wherein the UV lamp assembly remains powered throughsteps (a)-(i); a product of the ozone partial pressure in the plenum anda vertical height of the plenum is from 4 to 53 cm·Torr; theozone-containing gas contains 0.1 to 0.5 wt % of nitrogen gas; thehalogen-containing residues contain bromine; and/or the time period isfrom 15 to 60 seconds.
 9. The method of claim 6, wherein the UV lampassembly remains powered through steps (a)-(i); a product of the ozonepartial pressure in the plenum and a vertical height of the plenum isfrom 4 to 53 cm·Torr; the ozone-containing gas contains 0.1 to 0.5 wt %of nitrogen gas; the halogen-containing residues contain bromine; and/orthe time period is from 15 to 60 seconds.
 10. The method of claim 7,wherein the UV lamp assembly remains powered through steps (a)-(j); aproduct of the ozone partial pressure in the plenum and a verticalheight of the plenum is from 4 to 53 cm·Torr; the ozone-containing gascontains 0.1 to 0.5 wt % of nitrogen gas; the halogen-containingresidues contain bromine; and/or the time period is from 15 to 60seconds.
 11. A method of processing a semiconductor substrate in a degaschamber comprising a quartz window removably mounted over an opening ina top wall of the degas chamber and a UV lamp assembly disposed abovethe quartz window, the quartz window including a plenum and at least onegas passage in fluid communication with the plenum; an ozone source isin fluid communication with the at least one gas passage through a firstbranch of a branched gas line, gas flow through the first branchcontrolled by a first valve, the ozone source operable to supply anozone-containing gas to the plenum; the ozone source is in fluidcommunication with an inlet of a first vacuum pump through a secondbranch of the branched gas line, gas flow through the second branchcontrolled by a second valve, the first vacuum pump operable to evacuatethe plenum; an ozone destroying unit in fluid communication with anoutlet of the first vacuum pump through a third gas line, the ozonedestroying unit operable to destroy ozone flowing therethrough; theozone source is in fluid communication with the degas chamber through afourth gas line, gas flow through the fourth gas line controlled by afourth valve, the ozone source operable to supply an ozone-containinggas to the degas chamber; the degas chamber is in fluid communicationwith the inlet of the second vacuum pump through a fifth gas line, gasflow through the fifth gas line controlled by a fifth valve, the secondvacuum pump operable to evacuate the degas chamber; and an outlet of thesecond vacuum pump is in fluid communication with the ozone destroyingunit through a sixth gas line; the degas chamber further comprising acontroller operable to control the first, second, fourth, and fifthvalves, the ozone source and/or gas pressure in the plenum and in thedegas chamber, the method comprising: (a) closing the second, fourth andfifth valves with the controller, opening the first valve with thecontroller to supply the ozone-containing gas to the plenum andadjusting ozone partial pressure in the plenum with the controller toessentially block the UV light; (b) closing the first valve and openingthe fifth and second valves with the controller to evacuate the degaschamber; (c) transporting a semiconductor substrate into the degaschamber; (d) opening the first valve with the controller to evacuate theplenum; (e) closing the first and second valves and opening the fourthvalve with the controller to supply the degas chamber with anozone-containing gas; (f) generating O radicals in the chamber byirradiating the ozone-containing gas in the degas chamber with UV lightthrough the quartz window; (g) forming volatile byproducts by reactinghalogen-containing residues on the semiconductor substrate with the Oradicals for a time period and evacuating the volatile byproducts fromthe chamber; (h) closing the fourth and fifth valves and opening thefirst valve with the controller to supply the ozone-containing gas tothe plenum and adjusting ozone partial pressure in the plenum with thecontroller to essentially block the UV light; (i) closing the firstvalve and opening the second and fifth valves with the controller toevacuate the degas chamber; (j) transporting the semiconductor substrateout of the degas chamber; (k) repeating steps (a)-(j) with anothersemiconductor substrate.
 12. A method of processing a semiconductorsubstrate in a degas chamber comprising a quartz window removablymounted over an opening in a top wall of the degas chamber and a UV lampassembly disposed above the quartz window, the quartz window including aplenum and at least one gas passage in fluid communication with theplenum; an ozone source is in fluid communication with the at least onegas passage through a first branch of a branched gas line, gas flowthrough the first branch controlled by a first valve, the ozone sourceoperable to supply an ozone-containing gas to the plenum; the ozonesource is in fluid communication with an inlet of a first vacuum pumpthrough a second branch of the branched gas line, gas flow through thesecond branch controlled by a second valve, the first vacuum pumpoperable to evacuate the plenum; an ozone destroying unit in fluidcommunication with an outlet of the first vacuum pump through a thirdgas line, the ozone destroying unit operable to destroy ozone flowingtherethrough; the ozone source is in fluid communication with the degaschamber through a fourth gas line, gas flow through the fourth gas linecontrolled by a fourth valve, the ozone source operable to supply anozone-containing gas to the degas chamber; the degas chamber is in fluidcommunication with the inlet of the second vacuum pump through a fifthgas line, gas flow through the fifth gas line controlled by a fifthvalve, the second vacuum pump operable to evacuate the degas chamber;and an outlet of the second vacuum pump is in fluid communication withthe ozone destroying unit through a sixth gas line; the degas chamberfurther comprising a controller operable to control the first, second,fourth, and fifth valves, the ozone source and/or gas pressure in theplenum and in the degas chamber; wherein the quartz is synthetic quartzand/or the quartz window includes a first gas passage in fluidcommunication with the plenum operative to allow supply of theozone-containing gas to the plenum and a second gas passage in fluidcommunication with the plenum operative to allow evacuation of theplenum, the method comprising: (a) closing the second valve with thecontroller, opening the first, third and fourth valves with thecontroller to evacuate the degas chamber and to supply theozone-containing gas to the plenum and adjusting ozone partial pressurein the plenum with the controller to essentially block the UV light; (b)transporting a semiconductor substrate into the degas chamber; (c)closing the first valve and opening the second valve with the controllerto supply the degas chamber with an ozone-containing gas and to evacuatethe plenum; (d) generating O radicals in the chamber by irradiating theozone-containing gas in the degas chamber with UV light through thequartz window; (e) forming volatile byproducts by reactinghalogen-containing residues on the semiconductor substrate with the Oradicals for a time period and evacuating the volatile byproducts fromthe chamber; (f) closing the second valve and opening the first valvewith the controller to evacuate the degas chamber and to supply theozone-containing gas to the plenum and adjusting ozone partial pressurein the plenum with the controller to essentially block the UV light; (g)transporting the semiconductor substrate out of the degas chamber; (h)repeating steps (a)-(g) with another semiconductor substrate.
 13. Amethod of making a quartz window of a degas chamber in whichsemiconductor substrates are cleaned with an ozone-containing gas underillumination of UV light, the quartz window comprising: a bottomsurface, a top surface and a sidewall extending between the bottomsurface and the top surface; a plenum between the top and bottomsurfaces; and at least one gas passage in fluid communication with theplenum, the method comprising fusing together two quartz plates havingthe plenum and passage machined therein or mechanically clamping twoquartz plates together with a resilient seal ring sandwichedtherebetween thereby forming the plenum.